1. Field of the Invention
The present invention relates to a wireless power receiving device and a wireless power transmission device.
2. Description of the Related Art
In recent years, attention is paid to a wireless power transmission technology to externally supply power in a wireless mode without using a power cable in electric vehicles and mobile devices.
Since an occurrence of any abnormality in transmission of high power may cause breakage of a circuit element, such as a load, in such a wireless power transmission technology, there is an increasing demand to improve the safety of the entire device to which the wireless power transmission technology is applied.
In response to such a demand, for example, Japanese Unexamined Patent Application Publication No. 11-27870 proposes a charging device including an inverter circuit, a rectifier circuit, a booster circuit, a voltage checking circuit, and a short-circuiting circuit. The inverter circuit is provided at a primary coil (power feeding coil) side of a transformer. The inverter circuit performs frequency conversion of charge power to generate charge alternating current power and applies the charge alternating current power to the primary coil. The rectifier circuit is provided at a secondary coil (power receiving coil) side of the transformer. The rectifier circuit rectifies induced voltage occurring at the secondary coil to generate charge direct current power. The booster circuit is connected between the terminals of the secondary coil and increases the induced voltage occurring at the secondary coil to apply the induced voltage to the rectifier circuit. The voltage checking circuit checks the voltage of the direct current power and outputs a drive signal upon detection of a predetermined reference voltage value. The short-circuiting circuit causes short-circuit between the terminals of the secondary coil in response to the drive signal.
In the charging device having the above configuration, the rectifier circuit is composed of a bridge circuit including four diodes. Transistors are connected in parallel to two diodes in the rectifier circuit. More specifically, a collector terminal of the transistor is connected to a cathode of the corresponding diode and an emitter terminal of the transistor is connected to an anode of the corresponding diode. The two transistors are subjected to simultaneous turning on and off control. When the direct current power voltage is increased to the reference voltage, the two transistors are turned on, the short-circuit is caused between the terminals of the secondary coil, and the boost function of a capacitor is disabled to prevent the direct current power voltage from being increased to a value higher than the reference voltage value.
However, with the technology disclosed in Japanese Unexamined Patent Application Publication No. 11-27870, since the two transistors are simultaneously turned on to cause the short-circuit between the terminals of the secondary coil, the number of circuit elements and wiring lines is increased. Accordingly, there is a problem in that the circuit is complicated and the size of the circuit is increased.